1. Field
The present application relates to thermal management, and more particularly, to micro-scale cooling devices that use electrohydrodynamic (EHD, also known as electro-fluid-dynamic, EFD) technology to generate ions and electrical fields to control the movement of fluids, such as air, as part of a thermal management solution to dissipate heat.
2. Related Art
In general, electrohydrodynamic (EHD) technology uses corona discharge principles to move fluids (e.g., air molecules). Basic principles of EHD fluid flow are reasonably well understood by persons of skill in the art. Accordingly, a brief illustration of corona discharge principles in a simple two electrode system sets the stage for the more detailed description that follows.
With reference to the illustration in FIG. 1, corona discharge principles include applying a high intensity electric field between a first electrode 11 (often termed the “corona electrode,” the “corona discharge electrode,” the “emitter electrode” or just as the “emitter”) and a second electrode 12. Fluid molecules, such as surrounding air molecules, near the corona discharge region 18 become ionized and form a stream 14 of ions 16 that accelerate toward second electrode 12, colliding with neutral fluid molecules 22. During these collisions, momentum is imparted from the stream 16 of ions 14 to the neutral fluid molecules 22, inducing a corresponding movement of fluid molecules 22 in a desired fluid flow direction, denoted by arrow 13, toward second electrode 12. Second electrode 12 is variously referred to as the “accelerating”, “attracting”, “collector” or “target” electrode. While stream 14 of ions 16 are attracted to, and neutralized by, second electrode 12, neutral fluid molecules 22 move past second electrode 12 at a certain velocity. The movement of fluid produced by corona discharge principles has been variously referred to as “electric,” “corona” or “ionic” wind and has been defined as the movement of gas induced by the repulsion of ions from the vicinity of a high voltage discharge electrode.
Devices built using the principle of the ionic movement of a fluid are variously referred to in the literature as ionic wind machines, electric wind machines, corona wind pumps, electrostatic air accelerators, electro-fluid-dynamics (EFD) devices, electrostatic fluid accelerators (EFA), electrohydrodynamic (EHD) thrusters and EHD gas pumps. Some aspects of the technology have also been exploited in devices referred to as electrostatic air cleaners or electrostatic precipitators.
In the present application, embodiments of the devices illustrated and described herein are referred to as electrohydrodynamic fluid accelerator devices, also referred to in an abbreviated manner herein as “EHD devices”, and are utilized as a component in a thermal management solution to dissipate heat generated by an electronic circuit.